It's simple power chords, however I'm wondering (ignoring the 0-2-2 part) which way would be optimal to do this... would I use my index finger to hold down the E-3, my ring finger for A-5, and my pinky for D-5, or would I use my index for E-3 and my middle finger to to hold down both the A-5 and D-5? I'd like to use my index to mute the GBe so I can strum, however when I use the pinky and ring my ring finger tends to buzz because it can't go too far to the fret and it can't move too fast, but when I use the index and ring the ring finger tends to hold down the G sometimes, should I just practice and it'll eventually work out?

The first way is how I usually do it because my hands and fingers are small. Depends on how big your hands are also. You can use your ring and pinky to fret the notes or you can barre it with your ring finger. The second example you mention sounds painful. You must have some pretty wicked fingers to do that.

Sounds like you have having stretching problems with your pinky? and muting problems with higher strings.

As far as I'm aware, there's no real rule and you can do whichever way you feel most comfortable with. I Normally use Index, ring and pinky, except on on open position chords like E5 and A5 where I just use my index finger.

The first way is how I usually do it because my hands and fingers are small. Depends on how big your hands are also. You can use your ring and pinky to fret the notes or you can barre it with your ring finger. The second example you mention sounds painful. You must have some pretty wicked fingers to do that.

Sounds like you have having stretching problems with your pinky? and muting problems with higher strings.

I can do it fine, however my fingers are a little big and my ring finger is often pushed over by my pinky to the extent that it makes the string buzz.

Well, think of it like this. You need to be able to use both techniques later anyway - when you're doing other types of more complex chords and riffs. So if you can't play them well with fingers 134, you'll eventually run in to problems. Which one to choose as a standard is just preference, most like the 134.